1. Field of the Invention
The present invention relates to a fluid displacement apparatus, more particularly, to a valved discharge mechanism of a refrigerant compressor used in an automotive air conditioning system.
2. Description of the Prior Art
Valved discharged mechanisms of refrigerant compressors are well known in the prior art. For example, FIG. 1 depicts a valved discharge mechanism used in a refrigerant compressor as described in U.S. Pat. No. 4,978,285. As disclosed therein, a refrigerant compressor includes a compressor housing defining a compression chamber in which successive strokes of intake, compressing, and discharge of a refrigerant gas are repeatedly performed. Further, the compressor includes valve plate 65, which partitions the compression chamber and the discharge chamber, and a discharge valve assembly, which is mounted on an end surface of valve plate 65. Valve plate 65 has discharge hole 652 extending therethrough to allow communication of the compression chamber with the discharge chamber. The discharge valve assembly includes discharge reed valve 81 and valve retainer 80, which are secured together to end surface 65a of valve plate 65 by bolt 82. Discharge reed valve 81, which is made of an elastic material, regulates the flow of the refrigerant gas and sealingly engages end surface 65a of valve plate 65 when the operation of the compressor is stopped.
Valve retainer 80 limits the bending movement of discharge reed valve 81 in the direction in which the refrigerant gas exits the compression chamber and enters the discharge chamber through discharge hole 652. Discharge reed valve 81 has an elastic modulus which keeps discharge hole 652 closed until the pressure in the compression chamber reaches a predetermined value. In such an arrangement, discharge reed valve 81 strikes retainer 80 when it opens, and strikes end surface 65a of valve plate 65 when it closes. A compressor with such a discharge valve arrangement generates vibration and noise during operation of the compressor due to this striking. Vibrations caused by reed valve 81 striking end surface 65a of valve plate 65 are particularly disadvantageous, i.e., readily transmitted to the compressor housing.
One solution attempted by the assignee of the present application is depicted in FIG. 2. Though not prior art, this attempt is illustrative of progress in this area. There, valve plate 65 includes recessed portion 650 formed so that its depth increases with distance from point B, which is located on valve plate 65 and is spaced a distance L from bolt 82. Recessed portion 650 includes curved surface 651 surrounding discharge hole 652. When discharge reed valve 81 is in its closed position, it sealingly engages curved surface 651. Curved surface 651 has a radius of curvature R1, which defines the closing deformation of discharge reed valve 81.
Further, retainer 80 includes curved surface 80a having radius of curvature R2, which defines the opening deformation of discharge reed valve 81. Radius of curvature R1 is designed to be equal to or less than radius of curvature R2 so that when reed valve 81 closes, its elastic restoring force will not cause it to strike end surface 65a of valve plate 65. Curved surface 80a of retainer 80 begins curving away from valve plate 65 at point A, which is also spaced a distance L from bolt 82.
In this arrangement, the impact force with which discharge reed valve 81 strikes curved surface 65 1 of valve plate 65 is smaller than that which discharge reed valve 81 strikes retainer 80. This occurs because in the arrangement of FIG. 2, discharge reed valve 81 returns to its closed position primarily due to the pressure difference between the cylinder chamber and the discharge chamber, rather than because of the elastic restoring force of discharge reed valve 81. Therefore, noise and vibration which are caused by the striking of discharge reed valve 81 are reduced in comparison with the arrangement of FIG. 1. However, this arrangement does not account for noise and vibration which discharge reed valve 81 causes when discharge reed valve 81 strikes retainer 80.
As a result, vibration and noise still propagate to the passenger compartment.